Although other types are present, Meson is predominantly a database of directmate chess
problems from 2 to 5 moves. If a book is listed in the table above, it means that only the
directmates (from 2 to 5 moves) in that book have been added to Meson. Any other types present
in the book may or may not have been added to Meson.

As I haven't always noted in Meson the sources where problems have been quoted, inclusion of
a book in the table above does not guarantee that you will be able to search for it as a
‘quoter’ in the general search or via ‘Sources/Quoters’. Also, some books that
I have abstracted problems from are not in the table.